Arubi was the only thing standing in the way of Sundowns and a goal throughout the 120 minutes and then when the match did go to penalties, he brilliantly saved Hlompho Kekana's firmly-struck spot-kick towards the top right-hand corner.
And Mngqithi was full of praise for the Zimbabwean shot-stopper and was surprised he had to go down a division to get a team in recent years.
"We expected a very tough match because they are a very good team," the Masandawana mentor told SuperSport TV.
"Don't take them lightly. But I think credit today should be given to their goalkeeper. Washington was on top of his game today. He made some outstanding saves in areas where you thought he was dead and buried and he came out.
"I want to believe we tried to push them as much as we could. We created good moments. We had some calls where we think we could have got something out of them but in football you must always accept some of these things happening. We lost a game that i believed we played very well but unfortunately it wasn't to be and they must be congratulated They put up a very good fight and defender very well.
"And it was always going to be tough for us considering we had another tough match on Monday. Be that as it may we fought very hard. We pushed them. We created scoring opportunities. Washington was just there at the end of very ball and no wonder he was the man of the match.
"We don't have a chance. We have to pick ourselves up. We have another tough one again on Wednesday. It is important for us to come back quicker and not slumber. We're a big team. We've got the personnel. We were unfortunate today in that some of our key players had to pull out at the 11th hour - Denis and Mosa. But the truth must be told. We never really struggled in that regard. Because they made our life very difficult.
"I've always like Arubi. I've always believed he's a very good goalkeeper. And today he really showed his quality. And I am sure there are many other teams looking at him differently because he's always been a good goalkeeper. I was wondering why he had to slump down to NFD because he has always been one of the best goalkeepers in the country."